The invention relates to a safety belt buckle or lock, especially for motor vehicles, for receiving and locking an insertion tongue or lug, and includes a housing having an insertion passage for the insertion tongue that also contains a spring-loaded ejector, with a locking latch that is biased in an opening direction being pivotably mounted in the buckle such that in a locking position the locking latch engages the tongue recess, with the locking latch being secured in its locking position by a locking bar that is movably mounted in the housing at an angle to the insertion path for the buckle tongue, and with a sliding key that is guided transverse to a plane of movement of the locking latch for cancelling the locking action by actuating the locking bar, whereby to protect the buckle from shock, a compensating mass is mounted in the housing and in the direction of acceleration that is in the same direction as the pushing-in direction of the sliding key fixes the locking bar in position.
A safety belt buckle of this general type is disclosed inter alia in DE-OS 35 33 684, and in particular in the form of a so-called servo-lock where the locking latch that blocks the insertion tongue, due to the cinematics of the lock, has an opening bias or tendency, for which reason it is secured in the locked position by a special locking bar. The sliding key that is provided for opening the lock or buckle thereby merely actuates the locking bar, after the pivoting of which from the securing position into a release position, the locking latch swings out of the tongue recess, so that the buckle is unlocked.
If such a servo-lock is subjected to a tightening procedure, the buckle body is first subjected to an acceleration in the direction of the pushing-in movement of the sliding key; in so doing, the mass inertia of the locking bar leads to a retardation relative to the buckle body, and the resulting relative movement relative to the buckle body lets the locking bar pivot into its release position for the locking latch. At the end of the tightening procedure, the buckle body is suddenly decelerated, so that due to its own mass inertia, the sliding key slides into the buckle body and thus in turn actuates the locking bar to effect self-opening of the buckle. Consequently, tensioning movements of the buckle can result in automatic or self-opening of the buckle when the two types of acceleration occur.
With the known buckle, measures have already been taken for protecting the buckle against shock. For this purpose, with the known buckle a pivot lever that acts as a compensating mass is pivotably mounted in the buckle, but is connected to a push rod in a complicated and hence disadvantageous manner, with the push rod in turn linking the movements of the sliding key and the locking bar; accordingly, the pivot lever secures the locking bar in its locking position only indirectly via the push rod. Since for this reason the pivot lever must be matched not only to the mass of the locking bar but also to the movements of the push rod and the accelerating forces that act thereon, not only is the mass required for the pivot lever greater, but in addition the shock protection is composed of numerous components, the interaction of which must be accurately coordinated with one another. Inter alia, a retro fitting of existing buckles of the aforementioned type is therefore impossible.
It is therefore an object of the present invention to improve a buckle of the aforementioned general type in such a way that a functionally more reliable shock protection of the buckle is provided with few individual components.